Device for moving chain links in a resistance welding machine

ABSTRACT

A device is used for moving bent C-shaped links joined into a continuous chain to be welded in a resistance welding machine. The device has an inlet guide and an outlet guide, consisting, for example, of guiding rails. The device also has a saddle moving a link between tensioning tools and supporting it during the welding, as well as a transporting tool for the chain. The device is particularly characterized by the arrangement whereby the saddle is movable relatively to the guides substantially perpendicularly to the direction of movement of the chain link.

United States Patent Wust [72] Inventor: Toni Wust,

Ger y [73] Assignee: Meyer, Roth 8; Pastor, Cologne Raderberg, Germany22 Filed: Oct. 7, 1969 21 App1.No.: 864,407

Cologne-Bickendolf,

[30] Foreign Application Priority Data Oct. 9, 1968 Germany ..P 18 01955.1

[52] US. Cl ..59/31 [51] Int. Cl. ..B21l 3/02 [58] Field of Search..59/22, 31, 34, 29, 33

[56] References Cited UNITED STATES PATENTS 2,684,422 7/1954 Esser..59/31 3,389,552 6/1968 Kleine ..59/31 [451 Oct. 31, 1972 3,552,1181/1971 Reiter... ..59/31 FOREIGN PATENTS OR APPLICATIONS 1,340,0479/1963 France ..59/22 1,185,511 2/1959 France ..59/22 1,094,241 12/1967Great Britain ..59/31 Primary ExaminerCharles W. Lanham AssistantExaminerGene P. Crosby Attorney-Richards & Geier [5 7] ABSTRACT A deviceis used for moving bent C-shaped links joined into a continuous chain tobe welded in a resistance welding machine. The device has an inlet guideand an outlet guide, consisting, for example, of guiding rails. Thedevice also has a saddle moving a link between tensioning tools andsupporting it during the welding, as well as a transporting tool for thechain. The device is particularly characterized by the arrangementwhereby the saddle is movable relatively to the guides substantiallyperpendicularly to the direction of movement of the chain link.

8 Claims, 5 Drawing Figures P'A'TENTED 00131 I912 3.701. 253

SHEET 1 OF 4 FIG] a INVENTOR BY NJ 525 ma i-g ATTORNESS PATENTEDocm I972SHEET 2 OF 4 INVENTOR T. W051 BY ATTOYLNESS I PATENTED 0m 3 1 m2 SHEET 3[1F 4 PATENTED 7 3.701.253

saw u or 4 INVENTOR 7 Must ATTO I'LNEBS DEVICE FOR MOVING CHAIN LINKS INA RESISTANCE WELDING MACHINE This invention relates to a device formoving bent C- shaped links joined into a continuous chain for weldingthem in a resistance welding machine. The invention refers morespecifically to a device of this type having an inlet guide and anoutlet guide, consisting, for example, of guiding rails, as well as asaddle moving a link between tensioning tools and supporting it duringthe welding and a transporting tool for the chain.

In prior art machines of this type the guide and the saddle movejointly. The guide and the saddle are raised to move the chain into thewelding position and are then lowered so that the chain can betransported outside of the welding position.

The straight inlet and outlet guides extend always at an angle, so thatthe tensioning tools, such as the upsetting steels or tensioning jawscan grasp the link at its rounded portion, particularly in the case oflinks having a small pitch. The angle between the guides must besufficiently large to enable the chain to be guided without difficultiesaround the saddle located at the vertex of the angle. However, thegreater the angle, the greater must be the stroke of the two movabletensioning tools. On the other hand, the smaller the stroke of thetensioning tools, the easier and more reliable is the holding of thechain link being welded. A small stroke is particularly desirable forhydraulically operated tensioning tools so as to keep small theexpenditure of the hydraulic medium. However, a decisive advantage of asmall stroke is the gain in time consumption resulting therefrom.

An object of the present invention is to eliminate the drawbacks ofprior constructions by diminishing the stroke of the tensioning tools,namely, by arranging them closer to the welding location and providing aconstruction which even makes possible the use of a fixed tensioningtool.

Other objects of the present invention will become apparent in thecourse of the following specification.

In the accomplishment of the objectives of the present invention it wasfound desirable to make the saddle movable relatively to the guidessubstantially perpendicularly to the direction of movement of the link.This makes it possible to raise the chain above the vortex into thewelding position. In this location the angle between the incoming andoutgoing chain strands is smaller, so that it is possible to arrange thetensioning tools closer to the welding position. However, it is notnecessary to make smaller the angle between the ingoing and outgoingdirections, so that the sliding of the chain in the vortex is notdetrimentally affected. On the contrary, if desired, this angle can bemade larger than usual without it being necessary to arrange thetensioning tools at a greater distance from the welding position. Thusaccording to the present invention only the saddle is moved, but not theguides. This results in the substantial advantage that the masses whichare being moved are considerably smaller than those of prior artconstructions.

According to a further embodiment of the present invention, the chainguiding which heretofore extended perfectly straight, at least withinthe range of the saddle, can be made circular or elliptical, the crestof the ellipse being preferably located within the range of the saddle.In the case of such a continuously curved guiding, as compared to astraight guiding, the chain will not spring any more at the vortex, butwill always slide while lying upon the guide. Furthermore, by using acontinuously curved guide, it is possible to locate the entire incomingand outgoing guiding closer to the saddle, thereby saving space. Thisconstruction makes it also possible to diminish the stroke of thetensioning tools.

Preferably, the curved portion of the guide is continued as one or twostraight incoming and outgoing guides. These guides can be inclined orextend vertically.

It is known to make the guides of two ribs. However, in accordance withthe present invention the saddle may consist of a slide, preferably anarrow one, which can move out between these two ribs or be lowered intothem. When the slide is lowered, the chain is located between and uponthe curved ribs in the range under the welding position as well, so thatthe entire length of the chain is safely guided during transportation. Aslide which is thus constructed has a small mass and .therefore requiressmall actuating forces.

A further advantage results from the narrow construction of the slide,measured perpendicularly to the plane of the chain link being welded, inthat no dirt can be deposited between the slide and the back of thechain link, irrespective as to whether the engaging surface of the slideis fiat or curved.

It was found that prior saddles having a groove for guiding the back ofthe link, have the drawback that the groove is coated with weldingparticles with the results that the chain link is located incorrectly inthe welding position and that the transportation of the chain isdisturbed. Further difficulties are caused by burr chips and adhesivedirt residues which are deposited in the groove.

According to a further advantageous embodiment of the present inventionthe slide and the transporting tool are operated jointly, preferablyhydraulically. For that purpose, the slide and the transporting tool aremoved by separate double acting cylinders, the stroke of the cylinderactuating the transporting tool being shorter than that of the cylinderactuating the slide. The movement of the transporting tool in thedirection of transportation is either lagging and preferably equal inspeed to that of the slide, or is simultaneous and slower. This way ofoperating takes into consideration that the path of transportation ofthe chain is always smaller than the stroke of the slide, caused bydifferent locations of the chain when the slide is moved outwardly orlowered.

In prior machines the transporting tool consists of a finger whichextends into one of the chain links located in front of the one whichhas just been welded, the finger pulling the chain. However, when thewelding starts of an unwelded chain or when each n-th link is welded ina continuous operation, for example, in making chain pieces, then aftereach welding there is a change in the distance between the link whichwas just welded and the link engaged by the transportation finger, withthe result that during automatic chain pulling the location of thefinger must be continuously manually adjusted.

According to the present invention this drawback is eliminated byproviding a special transporting tool which is preferably jointlyactuated with the slide. This transporting tool consists of a forkedcasing and a doubly operating forked cylinder hydraulically operatedjointly with the transporting tool, the cylinder moving a forkedjawclamping the link. The forked jaw must be 'at least as long as two linkseparations, so that at least one link can be engaged independently ofthe location of the chain in the transporting tool. The joint actuation.is preferable in order that the forked jaw should be actuated firstduring the forward movement of the transporting tool and that it shouldbe released first during the rearward movement.

However, the forked jaw can be also moved by a forked cylinder operativesolely in the. clamping direction and a return spring arrangedpreferably between the forked jaw and the forked casing.

Movement between the slide and the forked casing can be transmittedpurely mechanically as well as mechanically hydraulically. Amechanical-hydraulic transmission of movement can take place with-theuse of a transporting tool constructed in accordance with the presentinvention and characterized by an outgoing "guide extending parallel orat an angle to the direction of movement of the slide and a driverconnected rigidly or pivotally with the slide. The driver carries apiston sliding in an intermediate cylinder of the forked casing, thestroke of which corresponds to the difference in stroke between theslide and the forked casing. Furthermore, a valve is provided havingsuch switching positions that in the clamping position of the forkedpiston in which the slide and the intermediate piston are located in thelower position, the upper sides of the slide piston and'the intermediatepiston, as well as the forked piston, are subjected to a predeterminedpressure, while the bottom side of the slide piston is subjected to aconsiderably lower pressure. In addition, the upper sides of the sidepiston and intermediate piston as well as that of the forked piston arenot subjected to pressure in their raised or rearward positions. Theforked piston is moved back by the return piston, while the slide pistonand the intermediate piston are in their upper positions and the forkedcasing is moved against a fixed stop. Finally, in the lowered or forwardposition the higher pressure is applied to the forked piston and theupper sides of the intermediate piston and the slide piston, while alower pressure is applied to the lower side of the slide piston, wherebythe forked piston is located in the champed position and theintermediate piston is located in its lower position, while: the slidepiston is moved downwardly.

In accordance with a further embodiment of the present inventionpertaining to a fixed and a movable tensioning tool, the guide and thesaddle, as well as the transporting tool, can be moved in the directionof movement of the tensioning tool with a lesser stroke than that of thetensioning tool, preferably one-half of the stroke. The guide, thesaddle and the transporting tool must be moved jointly, particularlywhen there is a common mechanical-hydraulic transmission of movementbetween the slide and the forked casing. If the stroke of the tensioningtool is twice as great as that of the guide, of the saddle and of thetransporting tool, the

' tensioning tool is preferably moved with a speed which is twice asgreat as the speed of the guide, the saddle and the transporting tool,so that the two tensioning tools will engage the chain link at the sametime, thereby avoiding the turning of the link.

More particularly, a device having a fixed and a movable tensioning toolcan be provided with a fixed lever engaging the movable tensioning tooland extend ing substantially perpendicularly to its direction ofmovement. A rod extending substantially parallel to the direction ofmovement of the tnesioning tool is pivoted to this lever, while theother end of the rod engages a part connecting the guide, the saddle andthe transporting tool. The lever is pivoted to the tensioning tool by anelongated hole so that when the tensioning tool is moved, the changes inlength between the moved end and the fixed end of the lever can becompensated. When the rod is pivoted to the middle of the lever, theguide, the saddle and the transporting tool will move substantially withone-half of the speed of the tensioning tool.

Various other slower or faster movements of the guide, the saddle andthe transporting tool relatively to the tensioning tool can be attainedby a device having two fixed two-armed rocking levers the adjacent endsof which are interconnected through elongated holes and which extendsubstantially perpendicularly to the movable tensioning tool. The freeend of one of these levers engages the movable tensioning tool throughan elongated hole, while the free end of the other lever is connected byan articulated rod with the part connecting the guide, the saddle andthe transporting tool. Different speeds are attained by suitablyselecting the lever lengths of the two rocking levers.

A movement of the guide, the saddle and the transporting tool or thetensioning tool, which has the same speed but extends over differentlengths, can be produced by a spring device which presses inthe weldingposition the guide, the saddle and the transporting tool or the partwhich joins them, and by an adjustable stop upon the rod to set thewelding position of the guide, the saddle and the transporting toolrelatively to the fixed tensioning tool, as well as a free motion driverlocated between the transmission lever or levers extending toward themovable tensioning tool and the rod end adjacent thereto. Preferably,the rod extends through a fixed part engaged by the spring device aswell as the stop.

In accordance with the present invention the greatest distance betweenthe movable tensioning tool on the one hand and the guide, the saddleand the transporting tool on the other hand, is set by an adjustabledriver stop at the end of the rod. The distance must be sufficientlygreat so that after the welding the upsetting movement can be carriedout. The free motion driver required for this purpose can be alsoconnected to the movable tensioning tool.

The invention will appear more clearly from the following detaileddescription when taken in connection with the accompanying drawings,showing, by way of example only, preferred embodiments of the inventiveidea.

IN THE DRAWINGS FIG. 1 is a diagrammatic sectional view of a devicehaving a common hydraulic actuating means;

FIG. 2 is a diagrammatic view, partly in section, of a device havingcommon mechanical-hydraulic actuating means;

FIG. 3 is a diagrammatic side view of a device having a fixed tensioningtool and a lever.

FIG. 4 is a diagrammatic side view of a device having two rockinglevers;

FIG. 5 is a diagrammatic side view of a device provided with a springarrangement.

The device shown in FIG. 1 has a slide 12 movable at right angles to thedirection of movement of a chain link 11. A guide 13 is uniformly curvedin the shape of a circular arc. The curved portion of the guide 13 iscontinued as a straight incoming guide 14 and a straight outgoing guide15. The guides 13, 14 and 15 have the shape of parallel rods. The slide12 can be moved outwardly between the guides or be lowered into them.The slide 12 is moved by a double acting cylinder 17, while thetransporting tool 16 is moved by a similar double acting cylinder 18,the stroke of the transporting cylinder 18 being shorter than the strokeof the slide cylinder 17. The common hydraulic device for actuating theslide 12 and the transporting tool 16 is only diagrammatically indicatedin FIG. 1. This hydraulic device can be used to vary the movement of thetransporting tool 16 in the direction of transportation relatively tothe movement of the slide 12, so that the tool will move either with alag and preferably with the same speed, or simultaneously and slowerthan the slide. The incoming guide 14 and the outgoing guide 15, andthus also the transporting tool 16 and the transporting cylinder 18,extend at an angle to the direction of movement of the slide 12, so thatthe chain can lie properly upon the guides 14 and 15.

FIG. 2 illustrates a device by means of which advantageous directions ofmovement can be carried out. These movements take place as follows:

At the end of the transportation movement of the chain 19, the slidepiston 21 located in the slide cylinder 20, will be in its lowermostposition, so that the slide 22 connected with the piston 21 is loweredbelow the rods within the guide 23. A driver 24 firmly connected withthe slide 22, is also so connected through an intermediate piston 25with a forked casing 26 having a forked piston 27, that the forkedcasing 26 can be moved relatively to the slide 22 according to thestroke of the intermediate piston 25 in the forked casing 26. During afurther movement of the slide piston 21 the intermediate piston 25 is inits end position in the forked casing 26, so that the forked casing 26is coupled with the slide 22. In this position the valve 28 of thehydraulic system is in the switching position A, so that pressureproduced in a pump 30 by a motor 29 and determined by a pressurelimiting valve 31, is applied to the upper surface of the slide piston21, the upper surface of the intermediate piston 25 and upon a surfaceof the forked piston 27. Considerably smaller pressure determined byanother pressure diminishing valve 32 is applied to the opposite side ofthe slide piston 21. The forked jaw 33 moved by the forked piston 27will thus firmly clamp the chain 19.

Due to the automatic connections of the machine, as soon as the chain 19is raised, the valve 28 will be moved into the switching position B. Oilin front of the upper surface of the slide cylinder 21 will be withoutpressure and the return spring 34 will open the forked jaw 33. The forceexerted upon the lower surface of the slide piston 21 and produced bypressure set by the pressure diminishing valve 32, will cause the slide22 to start its downward movement in the guide 23. After theintermediate piston 25 has completed its movement in the forked casing26, the casing 26 will be taken along. Finally, the unwelded chain linklying upon the guide 23 will be engaged and raised into the weldingposition. The upper end of the stroke of the slide 22 is determined by astop 35 of the forked casing 26. During welding the valve 28 is locatedin the switching position B FIG. 2 shows the device in the positionafter the completion of the welding. In this position the valve 28 islocated in the switching position C, the forked piston 27 is held andthe chain 19 is clamped. Thereupon the valve 28 is moved again into theswitching position A. Then pressure from the pressure limiting valve 31is increased over the upper space of the slide cylinder 20 in front ofthe forked piston 27 The upper surfaces of the slide piston 21 and theintermediate piston 25, as well as the surface of the forked piston 27,are so related to each other that the chain 19 remains clamped by theforked jaw 33. Due to this pressure, the slide 22 will start itslowering movement. Since the chain 19 will then lie upon the guide 23,the slide 22 will haveto move for a longer stretch than the forkedcasing 26. Consequently the intermediate piston 25 will move in theforked casing 26 down opposite to the stop and only then it will takealong the forked cashing 26 and the chain 19 in accordance with themovement of the slide 22. The operation is terminated in the lowerposition of the piston 21 and then the procedure is started again byswitching the valve 28 into the switching position 13.

FIG. 3 illustrates a device with a movable tensioning tool and a fixedtensioning tool which is simpler in construction than a device with twomovable tensioning tools. In accordance with this embodiment of thepresent invention the guide 36, the saddle 37 and the transporting tool(not shown) are movable in the direction of movement of the tensioningtool 38 by a stroke smaller than that of the tool to the extent of aboutone-half, relatively to the machine casing 39. A fixed lever 40 engagesthe tensioning tool 38 and extends perpendicularly to its direction ofmovement. A rod 41 pivoted to the lever 40 extends substantiallyparallel to the direction of movement of the tensioning tool and itsleft end (looking in the direction of FIG. 3) is connected to a part(not shown) which interconnects the guide 36, the saddle 37 and thetransporting tool (also not shown). In order to compensate for thechange in length between the fixed and the movably mounted ends of thelever 4D, which is produced during the movement of the tensioning tool38, the movably mounted end of the lever is connected to the tensioningtool 38 by an elongated hole 42. The difference in speeds between thetensioning tool 38 and guide 36, the saddle 37 as well as thetransporting tool, can be varied by the selection of the location of thepivot 43 connecting the lever 40 with the rod 41.

FIG. 4 illustrates another construction which makes it possible toproduce a greater speed of the guide, the saddle and the transportingtool relatively to the movable tensioning tool 44. In this constructionthe movable tensioning tool 44 is connected with two fixed twoannedrocking levers 47 and 48 the adjacent ends of which are joined throughan elongated hole 45. These levers extend substantially perpendicularlyto the movable tensioning tool 44 and their connection with the tool 44is effected through an elongated hole upon the free end of the upperlever 47. The free end of the other lever i8 is connected by a rod 49with the guide, the saddle and the transporting tool (not shown). Thespeeds of the tensioning tool 44, the guide, the saddle and thetransporting tool are fixed by a corresponding selection of the lengthsof the levers 47 and 48.

FIG; illustrates a construction which provides equal speeds for thetensioning tool 50, the guide, the saddle and the transporting tool (notshown). A rod 51 is connected with the guide, the saddle and thetransporting tool. The rod 51 carries a spring 52 which presses the rodin the direction toward the fixed tensioning tool 53 up to theadjustable stop 54 relatively to the machine casing 55. The rod 51 isconnected with the movable tensioning tool 50 through a driver 56. Thestop 54 is so set that when it is engaged the chain link 57 will alsoengage the fixed tensioning tool 53. During welding, namely, after thechain link 57 has been fixed between the tensioning tools 50 and 53 andalso during upsetting, that is when the tensioning tools 50 and 53 havemoved closer to each other, the driver 56 is freely movable upon the rod51. The adjustable driver stop 57' upon the end of the rod 51 is used toset the largest distance between the movable tensioning tool 50 on theone hand and the guide, the saddle and the transporting tool on theother hand.

As shown in FIG. 5 the tool 50 is connected by a rod to a piston 50'.The cylinder containing the piston 50' is provided with conduits onopposite sides to that the piston 50' is movable in opposite directions.Thus the piston 50' moves the guide 36, namely, both guiding partsagainst the fixed tensioning tool 53 and also moves the movable tool 50against the fixed tool 53. The movement of the guide 36 takes place froman initial position (not shown) in which the link 57 lies against thefixed tool 53 by the action of the spring 52. The guide 36 moves to theright by the action of the piston 50', the movable tool 50, the driver56 and the rod 51 against the action of the spring 52, whereby the endpositions of the guide 36 relatively to the casing floor 55 are providedby setting the stops 54 and 57'. Thus the guide 36 with all its partsincluding the slide is located initially at the fixed tool 53 while themovable tool 50 is pulled to the right by its piston. Only after thepiston 50 has moved beyond a certain point it moves in the second halfof its movement through the movable tool 5!) and the driver 56, as wellas the stop 57, the rod 51 and thus the entire guide with all thepertaining parts, so that in the end position of the piston 50' in whichit strikes a stop (not shown) the distance of the link 57 and of theguide 36 with all the parts connected therewith, from the fixed tool 53is the same as that from the movable tool 50. This position is shown inFIG. 5.

In the construction of FIG. 5 the rod 51 cooperates with a spring 52 anda stop 54. However, the rod 49 shown in FIG. 4 and the rod 41 shown inFIG, 3 can be also provided with a similar spring and stop.

While in the constructions of FIGS. 3, 4 and 5 the guide, the saddle andthe transporting tool were actuated by systems of levers and rods, theycan be also moved horizontally by a hydraulically operated cylinder orsome other suitable drive. Preferably the common movement of the guide,saddle and transporting tool is actuated jointly with the individualmovements of the saddle and the transporting tool.

I claim:

1. A device for moving a chain composed of interconnected bent C-shapedlinks for welding in a resistance welding machine, said devicecomprising a two part chain guide, the first part supporting the chainin aposition wherein one of its links is welded, the second part movingthe chain away from said position, tensioning tools holding a link inthe welding position, a transporting tool moving the chain along saidguide parts, a slide moving said link between said tensioning tools andsupporting it during welding, means moving said slide relatively to saidguide parts in a direction substantially perpendicular to the directionof movement of said chain, the two guide parts being symmetrical to aplane extending through the axis of the slide, and a drive comprising aforked casing, a forked piston located in said casing, a forked jawconnected with said piston, said drive actuating said piston jointlywith said transporting tool and causing said jaw to clamp the chain,said jaw having the shape of an elongated member the length of which isat least equal to that of two interconnected lines, said casing havingan elongated clamping surface located opposite said jaw.

2. A device in accordance with claim 1, said drive further comprising areturn spring between said jaw and said casing.

3. A device in accordance with claim 1, said drive further comprisingmeans connecting said slide with said forked casing for mechanicaltransmission of movement.

4. A device in accordance with claim 2, said drive further comprising adriver connected with said slide, a slide piston connected with saidslide, an intermediate piston connected with said driver, anintermediate casing enclosing said intermediate piston and connectedwith said forked casing, the stroke of said intermediate piston beingequal to the difference in strokes of the slide and the forked casing, astop located adjacent said forked casing, a valve having a plurality ofswitching positions and means connecting said valve with said pistonsand casings, whereby a. in one position of said valve which is theclamping position of the forked piston and in which the slide piston andthe intermediate pistonare located in their lowermost positions, theupper surfaces of the slide piston and of the intermediate piston andthe surfaces of the forked piston being subjected to predeterminedhydraulic pressure, while the lower surface of the slide piston issubjected to a substantially lesser hydraulic pressure;

. in another position of said valve which is the rising or rearwardposition of the device, the upper surfaces of the slide piston and ofthe intermediate piston and the surfaces of the forked piston are notsubjected to any hydraulic pressure, said return spring holding back theforked piston, the slide piston and the intermediate piston being intheir uppermost positions and the forked casing engaging said stop; and

c. in yet another position of said valve which is the lowered or forwardposition of the device, the

' forked piston and the upper surfaces of the intermediate piston and ofthe slide piston are subjected to higher hydraulic pressure and thelower surface of the slide piston is subjected to lower hydraulicpressure, the forked piston being in the clamping position, theintermediate piston being in the lowermost position and the slide pistonmoving downwardly.

5. A device in accordance with claim 1, wherein said tensioning toolsconsist of a fixed tensioning tool and a tensioning tool movablerelatively to said fixed tensioning tool, and having means moving saidguide, said slide and said transporting tool in the direction ofmovement of said movable tensioning tool but with a substantially lesserstroke.

6. A device in accordance with claim 5, wherein said 8. A device inaccordance with claim 5, comprising a driver stop connected with saidmovable tensioning tool.

1. A device for moving a chain composed of interconnected bent C-shapedlinks for welding in a resistance welding machine, said devicecomprising a two part chain guide, the first part supporting the chainin a position wherein one of its links is welded, the second part movingthe chain away from said position, tensioning tools holding a link inthe welding position, a transporting tool moving the chain along saidguide parts, a slide moving said link between said tensioning tools andsupporting it during welding, means moving said slide relatively to saidguide parts in a direction substantially perpendicular to the directionof movement of said chain, the two guide parts being symmetrical to aplane extending through the axis of the slide, and a drive comprising aforked casing, a forked piston located in said casing, a forked jawconnected with said piston, said drive actuating said piston jointlywith said transporting tool and causing said jaw to clamp the chain,said jaw having the shape of an elongated member the length of which isat least equal to that of two interconnected lines, said casing havingan elongated clamping surface located opposite said jaw.
 2. A device inaccordance with claim 1, said drive further comprising a return springbetween said jaw and said casing.
 3. A device in accordance with claim1, said drive further comprising means connecting said slide with saidforked casing for mechanical transmission of movement.
 4. A device inaccordance with claim 2, said drive further comprising a driverconnected with said slide, a slide piston connected with said slide, anintermediate piston connected with said driver, an intermediate casingenclosing said intermediate piston and connected with said forkedcasing, the stroke of said intermediate piston being equal to thedifference in strokes of the slide and the forked casing, a stop locatedadjacent said forked casing, a valve having a plurality of switchingpositions and means connecting said valve with said pistons and casings,whereby a. in one position of said valve which is the clamping positionof the forked piston and in which the slide piston and the intermediatepiston are located in their lowermost positions, the upper surfaces ofthe slide piston and of the intermediate piston and the surfaces of theforked piston being subjected to predetermined hydraulic pressure, whilethe lower surface of the slide piston is subjected to a substantiallylesser hydraulic pressure; b. in another position of said valve which isthe rising or rearward position of the device, the upper surfaces of theslide piston and of the intermediate piston and the surfaces of theforked piston are not subjected to any hydraulic pressure, said returnspring holding back the forked piston, the sliDe piston and theintermediate piston being in their uppermost positions and the forkedcasing engaging said stop; and c. in yet another position of said valvewhich is the lowered or forward position of the device, the forkedpiston and the upper surfaces of the intermediate piston and of theslide piston are subjected to higher hydraulic pressure and the lowersurface of the slide piston is subjected to lower hydraulic pressure,the forked piston being in the clamping position, the intermediatepiston being in the lowermost position and the slide piston movingdownwardly.
 5. A device in accordance with claim 1, wherein saidtensioning tools consist of a fixed tensioning tool and a tensioningtool movable relatively to said fixed tensioning tool, and having meansmoving said guide, said slide and said transporting tool in thedirection of movement of said movable tensioning tool but with asubstantially lesser stroke.
 6. A device in accordance with claim 5,wherein said means comprise a driver lever connected to said movabletensioning tool and extending substantially perpendicularly to itsdirection of movement, a movable rod connected to said lever andextending substantially parallel to the direction of movement of saidmovable tensioning member, a spring, a stop adjustably mounted upon saidrod and a driver stop adjustably mounted upon said rod.
 7. A device inaccordance with claim 6, wherein said driver stop is adjustably mountedupon said rod close to an end thereof.
 8. A device in accordance withclaim 5, comprising a driver stop connected with said movable tensioningtool.